• Journal of the Korean Ceramic Society
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• v.17 no.3
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• pp.121-128
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• 1980

In order to obtain the fundamental data for the preparation of ferroxplana $Zn_2Y(Ba_2Zn_2Fe_{12}O_{22})$, which is useful for GHz-band communication, the optimum coprecipitation condition of $Zn(NO_3)_2-6FeCl_3$ in $NH_4OH$ solution and the formation process of the hexagonal ferrite were investigated. By the hot-petroleum-drying and calcining the coprecipitated hydroxide mixture $Zn(OH)_2 +Ba(OH)_2+ 6Fe(OH)_3$, the fine and uniform powder was obtained , whose phase composition and microstructure were studied by X.R.D. and electron microscope. In results, it was found that $Zn_2Y$, BaM and $Zn_2W$ were the representative phases in calcined specimens whose activation energies of crystal growth were about 3, 8, 2.5, $5.4{\times}10^4$ J/mole , respectively. The sintered specimens would be appreciated as useful magnetic cores for the high frequency communication.

• Bulletin of the Korean Chemical Society
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• v.25 no.6
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• pp.859-864
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• 2004

The solid solutions of the $Sr_{1-x}Ba_xFeO_{3-y)$ system (x = 0.0, 0.1, 0.2 and 0.3) having a perovskite structure were prepared in air at 1423 K and then heat-treated in air (A), $O_2(O)\;and\;N_2(N)$ to examine possibility of controlling the nonstoichiometry and applicability as an additive for electrical conducting inorganic adhesives (ECIA). In the samples heated in $N_2$ stream, there existed almost no $Fe^{4+}$ ions, and at constant temperature their electrical conductivities were considerably lower than those of the samples heat-treated in air or $O_2.\; Sr_{0.8}Ba_{0.2}Fe^{3+}_{0.49}Fe^{4+}_{0.51}O_{2.76}$ (SB2-A) whose $Fe^{3+}/Fe^{4+}$ ratio was nearly 1 (0.96) and whose conductivity values (1.04 $ohm^{-1}cm^{-1}$ at 283 K and 1.88 $ohm^{-1}cm^{-1}$ at 673 K) were higher than any other samples, was found to be the best additive for ECIA.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.425-430
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• 1994

The effect of inhibitors and catalysts in the synthesis of 2-hydroxyethyl methacrylate(2-HEMA) was studied. As catalysts, triethylamine(TEA), $FeCl_3{\cdot}6H_2O$, $Cu(NO_3)_2{\cdot}2H_2O$, $AlCl_3$, $Na_2Cr_2O_7$were selected. p-Methoxyphenol (PMP) of aq. $NaNO_3$ solution was used as an inhibitor in polymerization. in aq. $NaNO_3$ inhibitor system, triethylamine (TEA), $FeCl_3{\cdot}6H_2O$, and $Na_2Cr_2O_7$, showed good catalytic effects. When p-methoxyphenol(PMP) was used as a polymerization inhibitor, the reaction was very sluggish and noneffective because the metal ion such as $Fe^{3+}$ or $Cr^{6+}$ was reduced by PMP. On the contrary, when aq. $NaNO_3$ was used as an inhibitor in polymerization, the reaction was very fast without deactivation of the metal catalysts.

• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.237-244
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• 2005

We prepared the cylindrical $\gamma-alumina$ pellets of 5 mm in diameter and 10 mm in average length using amorphous alumina and pore generating agent. The pellets were immersed in an aqueous solution of the mixture of $Fe(NO_{3})_{3}{\cdot}9H_{2}O$ and $CH_{3}COOH$. They were then hydrothermally treated at $200^{\circ}C$ for 3 h in autoclave, dried and calcined. For the application as an environmental catalyst, we investigated the decomposition characteristics of aniline and the initiation characteristics of $OH^{\cdot}$ conversion action in $O_{3}$ environment with or without the $Fe_{2}O_{3}$ supported y-alumina catalyst and $O_{3}$ molecule.

• Journal of the Korean Society of Safety
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• v.8 no.2
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• pp.3-9
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• 1993

For comparison, we used Ca and Mg as reducers to produce TiFe hydrogen stroage alloy from Fe and TiO$_2$by the Reduction-Diffusion process. The results obtained were as follow. \circled1 Ca was found to be effective both for reduction and diffusion processes. Moreover, Ca oxide was easily removed in an NH$_4$Cl solution after the reaction. \circled2 In the case of using Ca as a reducer, the Reduction-Diffusion process is considered to take place in the foiling three steps. First, TiO$_2$is reduced to Ti by Ca over 100$0^{\circ}C$. Second, the atomic Ti drifts in the Ca melt and meets Fe particles. Finally, the atomic Ti diffuses in to the Fe particles. \circled3 In the case of using Mg as a reducer, We found that the reduction reaction of TiO$_2$went well. But the reduced Ti scarcely diffused into Fe particles. This was probably because no Mg melt was formed due to the high vapor pressure of Mg.

• KSBB Journal
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• v.8 no.4
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• pp.409-414
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• 1993

This study was designed to reveal the conditions for $\beta$-glucosidase production from Aspergillus niger. The maximal enzyme production was obtained when the fungus was cultured at $30^{\circ}C$ for 5~6 days in the optimal medium containing 0.8% CMC, 0.5% beef extract, 0.3% Ca(NO3)2, 0.03% K2HPO4, 0.03% FeSO4, 0.05% Li2SO4, 0.2% tween 80, trace solution 1.0ml and initial pH 4.0, and then final enzyme activity under above conditions was 8.5-9.8 unit/ml culture filtrate.

• Journal of the Korean Electrochemical Society
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• v.23 no.4
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• pp.97-104
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• 2020

One of the main challenges of electrochemical water splitting technology is to develop a high performance, low cost oxygen-evolving electrode capable of substituting a noble metal catalyst, Ir or Ru based catalyst. In this work, CoFe₂O₄ nanoparticles with sub-44 nmsize of a inverse spinel structure for oxygen evolution reaction (OER) were synthesized by the injection of KNO₃ and NaOH solution to a preheated CoSO₄ and Fe(NO₃)₃ solution. The synthesis time of CoFe₂O₄ nanoparticles was controlled to control particle and crystallite size. When the synthesis time was 6 h, CoFe₂O₄ nanoparticles had high conductivity and electrochemical surface area. The overpotential at current denstiy of 10 mA/㎠ and Tafel slope of CoFe₂O₄ (6h) were 395 mV and 52 mV/dec, respectively. In addition, the catalyst showed excellent durability for 18 hours at 10 mA/㎠.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.555-560
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• 2014

In this paper, in order to develop outstanding Pb-free composition ceramics, the $Fe_2O_3$-doped ($Na_{0.525}K_{0.443}Li_{0.037}$)($Nb_{0.883}Sb_{0.08}Ta_{0.037}$)$O_3$ + 0.3 wt% $Bi_2O_3$ + x wt% $Fe_2O_3$ (x= 0~1.0 wt%)(abbreviated as NKL-NST) lead-free piezoelectric ceramics have been synthesized using the ordinary solid state reaction method. The effect of $Fe_2O_3$-doping on their microstructure and electrical properties were investigated. XRD diffraction pattern studies confirm that $Fe_2O_3$ completely diffused into the NKL-NST lattice to form a new stable soild solution with $Fe^{3+}$ entering the $Nb^{5+}$, $Sb^{5+}$ and $Ta^{5+}$ of B-site. And, phase structure of all the ceramics exhibited pure perovskite phase and no secondary phase was found in the ceramics. The ceramics doped with 0.6 wt% $Fe_2O_3$ have the optimum values of piezoelectric constant($d_{33}$), planar piezoelectric coupling coefficient($k_p$) and mechanical quality factor($Q_m$) : $d_{33}$ = 233 [pC/N], $k_p$= 0.44, $Q_m$= 95. These results indicate that the ($Na_{0.525}K_{0.443}Li_{0.037}$)($Nb_{0.883}Sb_{0.08}Ta_{0.037}$)$O_3$ +0.3 wt% $Bi_2O_3$ + 0.6 wt% $Fe_2O_3$ ceramic is a promising candidate for lead-free piezoelectric ceramics.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.3
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• pp.213-236
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• 2001

The ionic composition of soil solution is related to a nutrient uptake by plant. Many models for estimating ionic composition of solution have been developed, and most of them have been used for calculating a content of mineral and ionic species in a geochemical point of view. An approximation model considering both cation and anion in soil solution was developed. Variables such as pH, Eh, EC, cations(K, Ca, Mg. Na, Fe, Mn, Al, $NH_4{^+}$), anions(Si, S, P, CY, $NO_3{^-}$, $HCO_3{^-}$ and chemical equilibria of ionic species in soil solution were input into Excel sheet. The activities of soluble ion, ionpairs and complexes of input element were estimated by Newton-Raphson method using conditional equilibrium constant calculated by Davies equation and special models. Equilibrium contents of insoluble minerals and complexes were also calculated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.115-116
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• 2008

The ferroelectric vinylidene fluoride-trifluoroethylene ($VF_2$-TrFE) and $Al_2O_3$ passivation layer for the Metal/Insulator/Ferroelectric/Semiconductor (MIFS) structure were deposited using spin coating and remote plasma atomic layer deposition (RPALD), respectively. A 2.5 ~ 3 wt % diluted solution of purified vinylidene fluoride-trifluoroethylene ($VF_2$: TrFE=70:30) in a DMF solution were prepared and deposited on silicon wafer at a optimized spin speed. After annealing in a vacuum ambient at 150 ~ $200^{\circ}C$ for 60 min, upper insulator layer were deposited at temperature ranging from 100 ~ $150^{\circ}C$ by RPALD. We described electrical and structural properties of MIFS fabricated by spin coating and RPALD methods.